[KateBradbrook]

I am using driftFluxFoam and am struggling to set appropriate boundary condition for p_rgh. If I use fixedValue (of 0) or totalPressure, then I get the attached image with high velocities near bed where rho > rho_water due to the presence of the sediment. It works perfectly if I temporarily set the sediment density to the same as the water. Has anyone any ideas ?

[KateBradbrook]

Think, I've found a solution : I re-compiled solver with it creating a new variable rho_rel = (alpha1_*rhod_ + alpha2_*rhoc_)-rhoc_ to give the effective density of the sediment in water and then I could send this density to prghPressure